[gdal-dev] Question about gdaladdo and raster mosaicking

[Etienne Tourigny]

As was suggested, you could try using a mask instead.


On Thu, Jan 23, 2014 at 7:52 AM, Ammar <ammar83_h at yahoo.com> wrote:

> Chaitanya,
>
> Thank you very much for your reply and suggestion. I have used LZW with
> predictor 2 compression and added external overviews compressed in LZW too
> and the image came perfect. The only downside is the size of each of the
> images has expanded from approx. 2 GB to 18-20 GB. So now I have to choose
> between quality and size!
>
> Attached are two screen shots showing the difference.
>
> Thanks again!
>
> Regards,
> Ammar
>
>   ------------------------------
>  *From:* Chaitanya kumar CH <chaitanya.ch at gmail.com>
> *To:* ammar83_h at yahoo.com
> *Cc:* gdal dev <gdal-dev at lists.osgeo.org>
> *Sent:* Tuesday, January 21, 2014 6:27 PM
> *Subject:* Re: Question about gdaladdo and raster mosaicking
>
> Ammar,
> You are using lossy JPEG compression. I'm guessing that the white lines
> are are actually pixels with values near but not equal to 255. So, they are
> not treated as nodata pixels.
> My suggestion is to use another format with lossless compression for the
> 21 images or use a mask band if you prefer.
> Let me know how it goes.
> --
> Best regards,
> Chaitanya Kumar CH
> On 21-Jan-2014 5:31 pm, <ammar83_h at yahoo.com> wrote:
>
> Hello Chaitanya,
>
> I was looking online for solutions to my problem and I cam across some of
> your posts so I thought you might help me with my problem.
>
> I have 10,000+ TIFF files that I want to merge into one big Image and
> serve using GeoServer. I merged every 500 images at a time creating using
> gdalbuildvrt and gdal_translate along with JPEG compression creating 21
> TIFF files. I added overviews then to each of the new 21 files. When adding
> the images together, once directly as files using QGIS and another time as
> WMSs using GeoServer, I got white lines/gaps precisely at the border of
> ever 2 images. I thought the problem is with no data values but I decided
> to take another approach and merged all the 10,000 files into one huge
> image and this time I got one perfect image with no lines or gaps. I failed
> to create overviews for the big image because the process took days or
> gdaladdo running with no progress. I tested then on smaller images with and
> without overviews and the ones with no overview came perfect while the one
> with gdaladdo overviews came with the same problem of lines and gaps. The
> commands I m using are the following:
>
>  gdalbuildvrt -srcnodata 255 -vrtnodata 255 -a_srs EPSG:27700
> -input_file_list tiff_list.txt mosaic.vrt
>
> gdal_translate -of GTiff -co TILED=YES -co BIGTIFF=YES -co COMPRESS=JPEG
> -co JPEG_QUALITY=80 -co BLOCKXSIZE=512 -co BLOCKYSIZE=512 -co
> PHOTOMETRIC=YCBCR mosaic.vrt mosaic.tif
>
> gdaladdo mosaic.tif -r average --config COMPRESS_OVERVIEW JPEG --config
> JPEG_QUALITY_OVERVIEW 60 --config INTERLEAVE_OVERVIEW PIXEL --config
> PHOTOMETRIC_OVERVIEW YCBCR 2 4 8 16 32 64 128 256 512
>
> Any ideas, tips or recommendations would be appreciated!
>
> Best regards,
> Ammar
>
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>
>
>
>
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